Prophylaxis with single-dose doxycycline for the prevention of Lyme disease after an Ixodes scapularis tick bite

BACKGROUND

It is unclear whether antimicrobial treatment after an Ixodes scapularis tick bite will prevent Lyme disease.

METHODS

In an area of New York where Lyme disease is hyperendemic we conducted a randomized, double-blind, placebo-controlled trial of treatment with a single 200-mg dose of doxycycline in 482 subjects who had removed attached I. scapularis ticks from their bodies within the previous 72 hours. At base line, three weeks, and six weeks, subjects were interviewed and examined, and serum antibody tests were performed, along with blood cultures for Borrelia burgdorferi. Entomologists confirmed the species of the ticks and classified them according to sex, stage, and degree of engorgement.

RESULTS

Erythema migrans developed at the site of the tick bite in a significantly smaller proportion of the subjects in the doxycycline group than of those in the placebo group (1 of 235 subjects [0.4 percent] vs. 8 of 247 subjects [3.2 percent], P<0.04). The efficacy of treatment was 87 percent (95 percent confidence interval, 25 to 98 percent). Objective extracutaneous signs of Lyme disease did not develop in any subject, and there were no asymptomatic seroconversions. Treatment with doxycycline was associated with more frequent adverse effects (in 30.1 percent of subjects, as compared with 11.1 percent of those assigned to placebo; P<0.001), primarily nausea (15.4 percent vs. 2.6 percent) and vomiting (5.8 percent vs. 1.3 percent). Erythema migrans developed more frequently after untreated bites from nymphal ticks than after bites from adult female ticks (8 of 142 bites [5.6 percent] vs. 0 of 97 bites [0 percent], P=0.02) and particularly after bites from nymphal ticks that were at least partially engorged with blood (8 of 81 bites [9.9 percent], as compared with 0 of 59 bites from unfed, or flat, nymphal ticks [0 percent]; P=0.02).

CONCLUSIONS

A single 200-mg dose of doxycycline given within 72 hours after an I. scapularis tick bite can prevent the development of Lyme disease.

Arabidopsis transcriptome changes in response to phloem-feeding silverleaf whitefly nymphs. Similarities and distinctions in responses to aphids

Phloem-feeding pests cause extensive crop damage throughout the world, yet little is understood about how plants perceive and defend themselves from these threats. The silverleaf whitefly (SLWF; Bemisia tabaci type B) is a good model for studying phloem-feeding insect-plant interactions, as SLWF nymphs cause little wounding and have a long, continuous interaction with the plant. Using the Affymetrix ATH1 GeneChip to monitor the Arabidopsis (Arabidopsis thaliana) transcriptome, 700 transcripts were found to be up-regulated and 556 down-regulated by SLWF nymphs. Closer examination of the regulation of secondary metabolite (glucosinolate) and defense pathway genes after SLWF-instar feeding shows that responses were qualitatively and quantitatively different from chewing insects and aphids. In addition to the RNA profile distinctions, analysis of SLWF performance on wild-type and phytoalexin-deficient4 (pad4) mutants suggests aphid and SLWF interactions with Arabidopsis were distinct. While pad4-1 mutants were more susceptible to aphids, SLWF development on pad4-1 and wild-type plants was similar. Furthermore, although jasmonic acid genes were repressed and salicylic acid-regulated genes were induced after SLWF feeding, cytological staining of SLWF-infested tissue showed that pathogen defenses, such as localized cell death and hydrogen peroxide accumulation, were not observed. Like aphid and fungal pathogens, callose synthase gene RNAs accumulated and callose deposition was observed in SLWF-infested tissue. These results provide a more comprehensive understanding of phloem-feeding insect-plant interactions and distinguish SLWF global responses.

Spatial refuge from intraguild predation: implications for prey suppression and trophic cascades

The ability of predators to elicit a trophic cascade with positive impacts on primary productivity may depend on the complexity of the habitat where the players interact. In structurally-simple habitats, trophic interactions among predators, such as intraguild predation, can diminish the cascading effects of a predator community on herbivore suppression and plant biomass. However, complex habitats may provide a spatial refuge for predators from intraguild predation, enhance the collective ability of multiple predator species to limit herbivore populations, and thus increase the overall strength of a trophic cascade on plant productivity. Using the community of terrestrial arthropods inhabiting Atlantic coastal salt marshes, this study examined the impact of predation by an assemblage of predators containing Pardosa wolf spiders, Grammonota web-building spiders, and Tytthus mirid bugs on herbivore populations (Prokelisia planthoppers) and on the biomass of Spartina cordgrass in simple (thatch-free) and complex (thatch-rich) vegetation. We found that complex-structured habitats enhanced planthopper suppression by the predator assemblage because habitats with thatch provided a refuge for predators from intraguild predation including cannibalism. The ultimate result of reduced antagonistic interactions among predator species and increased prey suppression was enhanced conductance of predator effects through the food web to positively impact primary producers. Behavioral observations in the laboratory confirmed that intraguild predation occurred in the simple, thatch-free habitat, and that the encounter and capture rates of intraguild prey by intraguild predators was diminished in the presence of thatch. On the other hand, there was no effect of thatch on the encounter and capture rates of herbivores by predators. The differential impact of thatch on the susceptibility of intraguild and herbivorous prey resulted in enhanced top-down effects in the thatch-rich habitat. Therefore, changes in habitat complexity can enhance trophic cascades by predator communities and positively impact productivity by moderating negative interactions among predators.

Insecticide resistance in field populations of Asian citrus psyllid in Florida

BACKGROUND

Asian citrus psyllid (ACP), Diaphorina citri, is a major pest of citrus because it vectors the putative causal agent of huanglongbing disease. Insecticides are currently the basis of psyllid management programs, and the number of annual insecticide applications has increased significantly. In this paper, a series of investigations of insecticide resistance among field populations of adult and immature ACP in Florida is described.

RESULTS

In 2009, the highest level of resistance for adult ACP, as compared with the laboratory susceptible (LS) population, was found with imidacloprid with an LD(50) resistance ratio (RR(50) ) of 35 in one population. This was followed by chlorpyriphos (RR(50) = 17.9, 13.3, 11.8 and 6.9), thiamethoxam (RR(50) = 15 and 13), malathion (RR(50) = 5.4 and 5.0) and fenpropathrin (RR(50) = 4.8). In 2010, mortality of adults from all five sites sampled was lower than with the LS population at three diagnostic concentrations of each insecticide tested. Among nymph populations, indications of resistance were observed with carbaryl (RR(50) = 2.9), chlorpyriphos (RR(50) = 3.2), imidacloprid (RR(50) = 2.3 and 3.9) and spinetoram (RR(50) = 4.8 and 5.9). General esterase, glutathione S-transferase and monooxygenase levels were also elevated in field-collected adult and nymph ACP as compared with the LS population.

CONCLUSION

The present results suggest that varying levels of insecticide susceptibility exist in ACP populations across the citrus-growing areas of Florida. Increased levels of detoxifying enzymes in these populations may partially explain these differences. The present results indicate that insecticide resistance may become an emerging problem for ACP control if effective resistance management is not practiced.

Incompetence of deer as reservoirs of the Lyme disease spirochete

To determine whether deer may serve as reservoir hosts for the Lyme disease spirochete, we sought evidence of infection in nymphal Ixodes dammini derived from larvae that had engorged on white-tailed deer. A total of 19 deer were shot in two Lyme disease foci in Massachusetts during September 1986, the season in which larvae were most abundant. An average of 342 larval ticks of this species were collected from each deer. Of those that developed to the nymphal stage, the gut contents of 185 were examined for Borrelia burgdorferi by a direct fluorescent antibody test. Spirochetes were detected in about 1% of these nymphs, a rate of infection attributable to transovarial transmission. In contrast, infection was detected in 23% of 39 field-swept nymphal ticks of the same cohort that were collected during the following season. Although deer may be infested by numerous larval I. dammini, such ticks appear not to become infected by Lyme disease spirochetes.

Illustrated key to nymphs of the tick genus Amblyomma (Acari: Ixodidae) found in the United States

A dichotomous identification key, with important characters illustrated by scanning electron micrographs, is provided for nymphs of the 9 species of the genus Amblyomma occurring in the United States. Species included are A. americanum (L.), A. cajennense (F.), A. dissimile Koch, A. imitator Kohls, A. inornatum (Banks), A. longirostre (Koch), A maculatum Koch, A. rotundatum Koch, and A. tuberculatum Marx. Notes on the geographical distributions, medical and veterinary importance, and nymphal stage hosts are included for each species.

The neonicotinoid imidacloprid shows high chronic toxicity to mayfly nymphs

The present study evaluated the acute and chronic toxicity of imidacloprid to a range of freshwater arthropods. Mayfly and caddisfly species were most sensitive to short-term imidacloprid exposures (10 tests), whereas the mayflies showed by far the most sensitive response to long-term exposure of all seven arthropod species tested (28-d EC10 values of approximately 0.03 µg/L). The results indicated a high aquatic risk of chronic exposure of imidacloprid to mayflies.

Experimental transmission of Ehrlichia chaffeensis (Rickettsiales: Ehrlichieae) among white-tailed deer by Amblyomma americanum (Acari: Ixodidae)

Ehrlichia chaffeensis Anderson, Dawson & Wilson, causative agent of human (predominantly monocytic) ehrlichiosis, was successfully transmitted experimentally by Amblyomma americanum (L.) to white-tailed deer, Odocoileus virginianus (Zimmerman). Deer were needle-exposed intravenously to E. chaffeensis in tissue-culture canine macrophage (DH82) cells, and 11 d later were exposed to laboratory-reared A. americanum larvae, nymphs, and adults for acquisition feeding. Three months after this feeding, naive deer and dogs were exposed to recently molted nymphs and adults. Attempted reisolation of the pathogen by way of tissue culture was successful from one needle-exposed deer but not from the tick-exposed deer or dogs. Based on serologic evidence and polymerase chain reaction data, both nymphal and adult ticks transmitted E. chaffeensis to naive deer but not to dogs.

In planta expression or delivery of potato aphid Macrosiphum euphorbiae effectors Me10 and Me23 enhances aphid fecundity

The interactions between aphids and their host plants seem to be analogous to those of plant-microbial pathogens. Unlike microbial pathogen effectors, little is known about aphid effectors and their ability to interfere with host immunity. To date, only three functional aphid effectors have been reported. To identify potato aphid (Macrosiphum euphorbiae) effectors, we developed a salivary gland transcriptome using Illumina technology. We generated 85 million Illumina reads from salivary glands and assembled them into 646 contigs. Ab initio sequence analysis predicted secretion signal peptides in 24% of these sequences, suggesting that they might be secreted into the plant during aphid feeding. Eight of these candidate effectors with secretion signal peptides were functionally characterized using Agrobacterium tumefaciens-mediated transient overexpression in Nicotiana benthamiana. Two candidate effectors, Me10 and Me23, increased aphid fecundity, suggesting their ability to suppress N. benthamiana defenses. Five of these candidate effectors, including Me10 and Me23, were also analyzed in tomato by delivering them through the Pseudomonas syringae type three secretion system. In tomato, only Me10 increased aphid fecundity. This work identified two additional aphid effectors with ability to manipulate the host for their advantage.

Biases associated with several sampling methods used to estimate abundance of Ixodes scapularis and Amblyomma americanum (Acari: Ixodidae)

Several tick sampling methods were evaluated for ixodes scapularis Say and Amblyomma americanum (I.) in oak-dominated mixed hard-wood, pitch pine-dominated, and mixed hardwood and pine forests in coastal New Jersey. Walking surveys were more efficient for collecting I. scapularis adults than dragging by a factor of > 2:1. In contrast, drag sampling yielded nearly twice as many A. americanum adults compared with walking surveys. I. scapularis subadults were rarely collected during walking surveys. A. americanum nymphs were collected from drags approximately 3:1 over walking surveys. Twice as many A. americanum larvae were obtained from drags compared with walking surveys. All developmental stages of A. americanum responded positively to carbon dioxide. Pitfall traps and leaf litter samples collected very few ticks. Tick distribution among habitats varied significantly with the sampling method chosen, and the relative ranking of sites with respect to tick abundance varied depending on the stage of tick sampled. Failure to recognize the biases in these commonly used sampling techniques can potentially lead to incorrect conclusions that can have significant adverse public health consequences.

Maintenance of a laboratory colony of Cimex lectularius (Hemiptera: Cimicidae) using an artificial feeding technique

The in vitro maintenance technique described in this article has been used successfully to rear Cimex lectularius (L.) by feeding for >2 yr all nymphal stages and adults through parafilm "M" sealing film on different types of blood. Using this feeding technique, the subsequent egg production of female bedbugs was remarkably high. The blood was maintained at 37 degrees C to enhance the attachment of the bugs. The effect of anticoagulation methods for the blood meal was investigated, and heparinized blood was found the most suitable for feeding bugs. All stages of the bugs fed weekly on blood in the artificial feeding system remained attached for up to 0.5-1.0 h, until completion of their blood meals, and all reached engorged weights. More than 90% of the bugs fed artificially on whole blood, and they molted or laid eggs successfully.

Seasonal variation of transmission risk of Lyme disease and human babesiosis

The seasonal host-seeking pattern of nymphal Ixodes dammini infected with Babesia microti or Borrelia burgdorferi was determined on Nantucket Island, Massachusetts, during 1985. The peak period of host-seeking by infected nymphal I. dammini occurred in May and June. On a per person-hour basis, the number of infected ticks collected reached a maximum in May (Babesia = 17.3; Borrelia = 16.2). The number of infected ticks remained high in June, but decreased notably in July, August, and September. Transmission risk of the tick-borne etiologic agents of Lyme disease and human babesiosis in Massachusetts is greatest during the late spring-early summer months of May and June.

Survival and development of Ixodes scapularis (Acari: Ixodidae) under various climatic conditions in Ontario, Canada

Distribution of the blacklegged tick, Ixodes scapularis Say, is poorly defined in Ontario. An endemic population is known on Long Point peninsula, Lake Erie, Ontario, but I. scapularis adults have also been collected from other localities within the province. To test the hypothesis that distribution of the blacklegged tick is limited by cold climatic extremes, 35 fed female, 70 unfed adult, and 70 unfed nymphal I. scapularis were held in containers within four natural habitats on Long Point (42 degrees 36' N; 80 degrees 5' W) and at northern localities near Ottawa (45 degrees 27' N; 75 degrees 42' W), Hearst (49 degrees 40' N; 83 degrees 41' W), and Kenora (49 degrees 47' N; 94 degrees 29' W), Ontario, from early December 1991 until May 1993. At the northern localities, 84.8 and 30.5% of fed females and unfed adults survived overwinter, respectively. On Long Point, 56.4% of fed females and 23.6% of unfed adults successfully overwintered. Longevity of fed females and unfed adults was increased by > 2 mo at the northern localities compared with Long Point, although survival rates for unfed nymphs at the northern sites and on Long Point were similar. Females within the four habitats on Long Point, and at Kenora and Ottawa, laid eggs from late April to mid-May, whereas eggs were deposited in late June at Hearst. Emergence of larvae from eggs began in late July or early August on Long Point and at Ottawa. Larvae were first observed in early October at Kenora, and no larvae emerged during 1992 at Hearst. Some eggs that overwintered during 1992-1993 at the northern sites were viable; however, hatching rate was < 10%. The minimum duration of the life cycle of I. scapularis is extended when ticks are introduced into regions of the province with seasonal degree-day accumulations lower than those observed on Long Point. Delays in deposition of eggs and emergence of larvae at Hearst and Kenora were likely a result of insufficient accumulation of degree-days above threshold temperatures for development in 1992. Though some eggs can overwinter successfully, suggesting that latitude-related reduction in seasonal temperature may not limit distribution of this tick in Ontario, hatchability was low. This factor, combined with innate incremental mortality at each instar, difficulty in finding a mate, and low density of medium to large mammal hosts for adults, may mitigate against establishment of I. scapularis by introduction of individual ticks into certain northern regions.

Survival of Ixodes ricinus (Acari: Ixodidae) under challenging conditions of temperature and humidity is influenced by Borrelia burgdorferi sensu lato infection

ABSTRACT To determine whether Borrelia burgdorferi sensu lato (s.l.) influences tick survival under thermohygrometric stress, Ixodesricinus (L.) (Acari: Ixodidae) questing ticks were tested under various relative humidities (13, 32, 51.5, 61, and 89% RH) at two different temperatures (12.5 and 25 degrees C) and investigated for Borrelia infection. Survival rate of females was highest (77.6%), followed by males (51.6%), and nymphs (43.2%). The thermohygrometric factor that most importantly determined survival was saturation deficit (SD). As SD increased, tick survival rate decreased in all stages. Among the 1,500 ticks tested for B. burgdorferi s.l., 34.8% (n = 522) were infected. Adult infection rate (39.6%) was higher than that of nymphs (25.5%). Infection load in real-time polymerase chain reaction ranged from 1 to 1.2 million spirochetes per tick. B. afzelii (39.7%), B. burgdorferi sensu stricto (12.1%), B. garinii (37.9%), B. myamotoi (3.6%), and B. valaisiana (23.8%) were recorded. B. garinii infected significantly less nymphs than adults whereas B. afzelii displayed the opposite trend. Survival rate of nymphal and adult I. ricinus was significantly enhanced by infection by B. burgdorferi s.l. (Chi(2): nymph, P = 0.008; adult, P = 0.021). In adults, a negative effect of infection on tick survival was observed when spirochete load overcame a threshold estimated at 160,000 spirochetes per tick but not in nymphs. Moreover, ticks infected by B. afzelii survived better than other ticks (infected by other genospecies or not). The results here indicate that infection by B. burgdorferi s.l., and more specifically infection by B. afzelii, confers survival advantages to I. ricinus under challenging thermohygrometric conditions.

Cutting edge: Immunity against a "silent" salivary antigen of the Lyme vector Ixodes scapularis impairs its ability to feed

Ixodes scapularis ticks transmit the Lyme disease agent in the United States. Although strong antitick immunity mediates tick rejection by certain vertebrates, only a few Ags have been molecularly characterized. We show that guinea pig vaccination against a secreted tick salivary immunomodulator, sialostatin L2, can lead to decreased feeding ability of I. scapularis nymphs. Increased rejection rate, prolonged feeding time, and apparent signs of inflammation were observed for nymphs attached to vaccinated animals, indicating a protective host immune response. Interestingly, sialostatin L2 humoral recognition does not take place upon repeated tick exposure in control animals, but only in the vaccinated animals that neutralize sialostatin L2 action. Therefore, we demonstrate an essential sialostatin L2 role upon nymphal infestation that can be blocked by vertebrate immunity and propose the discovery of similarly "silent" Ags toward the development of a multicomponent vaccine that will protect against tick bites and the pathogens they transmit.

Tick burden on European roe deer (Capreolus capreolus)

In our study we assessed the tick burden on roe deer (Capreolus capreolus L.) in relation to age, physical condition, sex, deer density and season. The main objective was to find predictive parameters for tick burden. In September 2007, May, July, and September 2008, and in May and July 2009 we collected ticks on 142 culled roe deer from nine forest departments in Southern Hesse, Germany. To correlate tick burden and deer density we estimated deer density using line transect sampling that accounts for different detectability in March 2008 and 2009, respectively. We collected more than 8,600 ticks from roe deer heads and necks, 92.6% of which were Ixodes spp., 7.4% Dermacentor spp. Among Ixodes, 3.3% were larvae, 50.5% nymphs, 34.8% females and 11.4% males, with significant seasonal deviation. Total tick infestation was high, with considerable individual variation (from 0 to 270 ticks/deer). Adult tick burden was positively correlated with roe deer body indices (body mass, age, hind foot length). Significantly more nymphs were found on deer from forest departments with high roe deer density indices, indicating a positive correlation with deer abundance. Overall, tick burden was highly variable. Seasonality and large scale spatial characteristics appeared to be the most important factors affecting tick burden on roe deer.

Preliminary assessment of microbiome changes following blood-feeding and survivorship in the Amblyomma americanum nymph-to-adult transition using semiconductor sequencing

The physiology of ticks supports a diverse community of non-pathogenic and pathogenic organisms. This study aims to initially characterize the microbial community present within colony-reared Amblyomma americanum using PCR of the variable region 5 of the 16S rRNA gene followed by semiconductor sequencing and classification of sequence data using the Ribosomal Database Project and MG-RAST analysis tools. Comparison of amplicon library datasets revealed changes in the microbiomes in newly engorged nymphs, newly-molted adults, and aged adults, as well as ticks exposed to different environmental conditions. These preliminary data support the concept that microbe survivorship and diversity are partially dependent upon environmental variables and the sequence of blood feeding, molting, and aging. The maintenance and/or emergence of pathogens in ticks may be dependent in part on temporal changes in the microbial community of the tick microbiome.

Symbiotic bacteria associated with stomach discs of human lice

The symbiotic bacteria associated with the stomach disc, a large aggregate of bacteriocytes on the ventral side of the midgut, of human body and head lice were characterized. Molecular phylogenetic analysis of 16S rRNA gene sequences showed that the symbionts formed a distinct and well-defined clade in the Gammaproteobacteria. The sequences exhibited AT-biased nucleotide composition and accelerated molecular evolution. In situ hybridization revealed that in nymphs and adult males, the symbiont was localized in the stomach disc, while in adult females, the symbiont was not in the stomach disc but in the lateral oviducts and the posterior pole of the oocytes due to female-specific symbiont migration. We propose the designation "Candidatus Riesia pediculicola" for the louse symbionts.

Survival and development of the different life stages of Ixodes scapularis (Acari: Ixodidae) held within four habitats on Long Point, Ontario, Canada

From November 1989 to April 1993, blood-fed females and unfed adults and nymphs of lxodes scapularis Say were maintained in housings within 4 different habitats on Long Point, Ontario, Canada, to evaluate the effects of habitat on tick development. More fed females survived the winter within the maple forest (75.6%) than the cottonwood dune (36.1%), whereas 52.8-62.0% survived the winter within the 2 remaining habitats. The proportions of females that laid eggs within the maple forest (90.3%), oak savannah (83.9%), and white pine habitats (78.4%) were similar and greater than in the cottonwood dune (53.8%). In each habitat and all years, females began laying eggs during late April or early May. The time of egg deposition was consistent whether females fed in November and overwintered, or fed during April of the subsequent year. Significantly more eggs hatched within the maple forest (96.4%) and white pine (79.3%) than in the oak savannah (3.8%) or cottonwood dune habitats (0.0%). Hatch occurred in mid- to late July each year. The proportion of unfed I. scapularis adults that survived the winter was not significantly different among the 4 habitats. Unfed adults held in the oak savannah and cottonwood dune habitats died by early June, whereas ticks survived until late June or early July within the maple forest and white pine habitats. Unfed nymphs survived an average of 3.4 mo (range, 0.5-5.5) longer than unfed adults. Fed larvae placed in the field from 22 April to 3 July 1992 molted or died that year. In contrast, 66.7 and 100% of fed larvae placed in the field between 15 and 28 July, and after 28 July, respectively, overwintered before molting. More larvae successfully molted before overwintering (46.9%) than did those that overwintered (17.9%). The proportion of larvae that successfully molted was greatest within the maple forest and least within the cottonwood dune. Fed nymphs placed in the field from 22 April to 4 June molted or died in 1992, whereas 53.6 and 99.2% of fed nymphs placed in the field between 17 June and 28 July, and later than 28 July, respectively, overwintered before molting. Over all habitats, the proportion of nymphs that molted successfully was similar for those that overwintered (43.5%) and those that did not (36.0%). The proportion of nymphs that molted successfully was greatest in the maple forest (60.6%) and least within the cottonwood dune (13.3%). Differences in seasonal extremes of vapor pressure deficits among habitat types were likely responsible for habitat-specific differences in survival of I. scapularis. Based on observations on captive I. scapularis, the life cycle of this tick on Long Point is completed in 3 or 4 yr.

Population regulation in ticks: the role of acquired resistance in natural and unnatural hosts

Attachment, engorgement and subsequent development of successive infestations of Ixodes trianguliceps larvae and nymphs on natural hosts, Apodemus sylvaticus, and unnatural hosts, laboratory mice, are compared. In laboratory mice, primary infestations above a threshold level of about 10 ticks elicit an immunological response which reduces, in a density-dependent manner, the rate of successful tick engorgement during subsequent infestations. In contrast, in A. sylvaticus successive infestations of larvae result in unchanged or slightly improved survival through to nymphs. The relevance of these results to the concept of host-parasite co-evolution and to tick population regulation is discussed.

Spatiotemporal patterns and dispersal of stink bugs (Heteroptera: Pentatomidae) in peanut-cotton farmscapes

In the southeast United States, a field of peanuts, Arachis hypogaea L., is often closely associated with a field of cotton, Gossypium hirsutum L. The objective of this 4-yr on-farm study was to examine and compare the spatiotemporal patterns and dispersal of the southern green stink bug, Nezara viridula L., and the brown stink bug, Euschistus servus (Say), in six of these peanut-cotton farmscapes. GS(+) Version 9 was used to generate interpolated estimates of stink bug density by inverse distance weighting. Interpolated stink bug population raster maps were constructed using ArcMap Version 9.2. This technique was used to show any change in distribution of stink bugs in the farmscape over time. SADIE (spatial analysis by distance indices) methodology was used to examine spatial aggregation of individual stink bug species and spatial association of the two stink bug species in the individual crops. Altogether, the spatiotemporal analyses for the farmscapes showed that some N. viridula and E. servus nymphs and adults that develop in peanuts disperse into cotton. When these stink bugs disperse from peanuts into cotton, they aggregate in cotton at the interface, or common boundary, of the two crops while feeding on cotton bolls. Therefore, there is a pronounced edge effect observed in the distribution of stink bugs as they colonize the new crop, cotton. The driving force for the spatiotemporal distribution and dispersal of both stink bug species in peanut-cotton farmscapes seems to be availability of food in time and space mitigated by landscape structure. Thus, an understanding of farmscape ecology of stink bugs and their natural enemies is necessary to strategically place, in time and space, biologically based management strategies that control stink bug populations while conserving natural enemies and the environment and reducing off-farm inputs.

Identification and characterization of Ixodes scapularis antigens that elicit tick immunity using yeast surface display

Repeated exposure of rabbits and other animals to ticks results in acquired resistance or immunity to subsequent tick bites and is partially elicited by antibodies directed against tick antigens. In this study we demonstrate the utility of a yeast surface display approach to identify tick salivary antigens that react with tick-immune serum. We constructed an Ixodes scapularis nymphal salivary gland yeast surface display library and screened the library with nymph-immune rabbit sera and identified five salivary antigens. Four of these proteins, designated P8, P19, P23 and P32, had a predicted signal sequence. We generated recombinant (r) P8, P19 and P23 in a Drosophila expression system for functional and immunization studies. rP8 showed anti-complement activity and rP23 demonstrated anti-coagulant activity. Ixodes scapularis feeding was significantly impaired when nymphs were fed on rabbits immunized with a cocktail of rP8, rP19 and rP23, a hall mark of tick-immunity. These studies also suggest that these antigens may serve as potential vaccine candidates to thwart tick feeding.

Geography, deer, and host biodiversity shape the pattern of Lyme disease emergence in the Thousand Islands Archipelago of Ontario, Canada

In the Thousand Islands region of eastern Ontario, Canada, Lyme disease is emerging as a serious health risk. The factors that influence Lyme disease risk, as measured by the number of blacklegged tick (Ixodes scapularis) vectors infected with Borrelia burgdorferi, are complex and vary across eastern North America. Despite study sites in the Thousand Islands being in close geographic proximity, host communities differed and both the abundance of ticks and the prevalence of B. burgdorferi infection in them varied among sites. Using this archipelago in a natural experiment, we examined the relative importance of various biotic and abiotic factors, including air temperature, vegetation, and host communities on Lyme disease risk in this zone of recent invasion. Deer abundance and temperature at ground level were positively associated with tick abundance, whereas the number of ticks in the environment, the prevalence of B. burgdorferi infection, and the number of infected nymphs all decreased with increasing distance from the United States, the presumed source of this new endemic population of ticks. Higher species richness was associated with a lower number of infected nymphs. However, the relative abundance of Peromyscus leucopus was an important factor in modulating the effects of species richness such that high biodiversity did not always reduce the number of nymphs or the prevalence of B. burgdorferi infection. Our study is one of the first to consider the interaction between the relative abundance of small mammal hosts and species richness in the analysis of the effects of biodiversity on disease risk, providing validation for theoretical models showing both dilution and amplification effects. Insights into the B. burgdorferi transmission cycle in this zone of recent invasion will also help in devising management strategies as this important vector-borne disease expands its range in North America.

[Light microscopic studies on the development of Theileria annulata (Dschunkowsky and Luhs, 1904) in Hyalomma anatolicum excavatum (Koch, 1844). I. The development in the gut of engorged nymphs (author's transl)]

A laboratory strain of H. a. excavatum was selected on high susceptibility for T. annulata through several generations. Giemsa-stained smears and wet smears of gut and gut content were studied. After engorgement of erythrocytic stages of T. annulata by the nymphs the following development was observed: 1. Erythrocytic merozoites developed to slender, spindleshaped "microgamonts" in the gut 24 to 96 hours after repletion (p. repl.). Spherical stages with a conspicuous spike developed at the same time and earlier. The "microgamonts" then form up to 4 nuclei and several flagella-like appendices. Filiform "microgametes" obviously develop from the "microgamonts". In addition, spherical stages, i.e. "macrogametes", occur. 2. Spherical "zygotes" with a vacuole-like center appear in the epithelial cells of the gut from day 5 p. repl. These "zygotes" increase steadily in size and then stain more intensely up to day 12 p. repl. 3. From day 12 p. repl. the spherical "Zygotes" change to elongate forms by a continuing process of folding. Finally, from day 13 p. repl., they extend to clubshaped kinetes. These kinetes move actively by gliding within the gut cells and from day 17 p. repl. in the haemolymph. It could not be decided yet whether these kinetes are oo- or sporokinetes.